Cancer is the second leading cause of death in the United States, exceeded only by heart disease. (Cancer Facts and Figures 2004, American Cancer Society, Inc.) Despite recent advances in cancer diagnosis and treatment, surgery and radiotherapy may be curative if a cancer is found early, but current drug therapies for metastatic disease are mostly palliative and seldom offer a long-term cure. Even with new chemotherapies entering the market, the need continues for new drugs effective in monotherapy or in combination with existing agents as first line therapy, and as second and third line therapies in treatment of resistant tumors.
Cancer cells are by definition heterogeneous. For example, within a single tissue or cell type, multiple mutational ‘mechanisms’ may lead to the development of cancer. As such, heterogeneity frequently exists between cancer cells taken from tumors of the same tissue and same type that have originated in different individuals. Frequently observed mutational ‘mechanisms’ associated with some cancers may differ between one tissue type and another (e.g., frequently observed mutational ‘mechanisms’ leading to colon cancer may differ from frequently observed ‘mechanisms’ leading to leukemias). It is therefore often difficult to predict whether a particular cancer will respond to a particular chemotherapeutic agent. (Cancer Medicine, 5th Edition, Bast et al. eds., B. C. Decker Inc., Hamilton, Ontario)
Components of cellular signal transduction pathways that regulate the growth and differentiation of normal cells can, when dysregulated, lead to the development of cellular proliferative disorders and cancer. Mutations in cellular signaling proteins may cause such proteins to become expressed or activated at inappropriate levels or at inappropriate times during the cell cycle, which in turn may lead to uncontrolled cellular growth or changes in cell-cell attachment properties. For example, dysregulation of receptor tyrosine kinases by mutation, gene rearrangement, gene amplification, and overexpression of both receptor and ligand has been implicated in the development and progression of human cancers.
The c-Met receptor tyrosine kinase is the only known high-affinity receptor for hepatocyte growth factor (HGF), also known as scatter factor. Binding of HGF to the c-Met extracellular ligand-binding domain results in receptor multimerization and phosphorylation of multiple tyrosine residues in the intracellular portion of c-Met. Activation of c-Met results in the binding and phosphorylation of adaptor proteins such as Gab-1, Grb-2, Shc, and c-Cbl, and subsequent activation of signal transducers such as PI3K, PLC-γ, STATs, ERK1 and 2 and FAK. c-Met and HGF are expressed in numerous tissues, and their expression is normally confined predominantly to cells of epithelial and mesenchymal origin, respectively. c-Met and HGF are dysregulated in human cancers and may contribute to dysregulation of cell growth, tumor cell dissemination, and tumor invasion during disease progression and metastasis (See, e.g., Journal of Clinical Investigation 109: 863-867 (2002) and Cancer Cell pp 5-6 Jul. 2004). c-Met and HGF are highly expressed relative to surrounding tissue in numerous cancers, and their expression correlates with poor prognosis and lack of response to standard clinical treatments. (See, e.g., Journal of Cellular Biochemistry 86: 665-677 (2002); Int. J. Cancer (Pred. Oncol.) 74: 301-309 (1997); Clinical Cancer Research 9: 1480-1488 (2003); and Cancer Research 62: 589-596 (2002)). Without intending to be bound by theory, c-Met and HGF may protect tumors against cell death induced by DNA-damaging agents and, as such, may contribute to chemoresistance and radioresistance of tumors. Without intending to be limited by any theory, inhibitors of c-Met may be useful as therapeutic agents in the treatment of proliferative disorders including breast cancer. (See, e.g., Cancer and Metastasis Reviews 22: 309-325 (2003)). Accordingly, new compounds and methods for modulating these factors and treating cancer are needed. The present invention addresses these needs.